This invention relates to optical viewing devices for the visually handicapped, and more particularly, it relates to apparatus which permits visually handicapped people to read ordinary textual materials.
A wide variety of devices is used to project images of transparent or opaque materials and of various artifacts so that an enlargement of the original is perceived. Thus, Erban U.S. Pat. No. 2,711,669 shows a projection apparatus for providing images of reduced materials on a viewing screen. The Erban device is used to view specially prepared microscopic reproductions of printed material onto a viewing screen. Another example of a device for viewing specially prepared microscopic opaque materials is shown in Erban U.S. Pat. No. 3,354,775, and devices for viewing transparencies are well known, as exemplified by Hopkins U.S. Pat. Nos. 2,322,023 and 2,937,569. A device for greatly enlarging profiles of physical optics is exemplified in Bausch et al U.S. Pat. No. 2,064,368.
The foregoing apparatus are not suited for viewing ordinary textual materials. They require additional steps to prepare a special copy.
The desirability of machines for reading ordinary materials has, of course, been recognized. One approach to the problem, Frank et al U.S. Pat. No. 2,720,136, shows a projector which rests on top of a book or other textual material. While permitting the enlargement of such ordinary material, this device does not produce a very bright or a very greatly enlarged image on the screen. Moreover, it requires that the entire head be raised and lowered on the material, and it can be difficult conveniently to move the textual material so that a line can be readily scanned. One approach to overcoming the disadvantages of the foregoing projector is shown in Cinque U.S. Pat. No. 3,817,613. In Cinque the head is no longer in contact with the material to be read, since a vertically moveable head is utilized. Unfortunately, in practical use this device exhibits a number of deficiencies which appear to have deterred its acceptance. The fact that the head is vertically displaceable means that either a long focus imaging lens must be used with the consequent production of a dimmer image or, alternatively, the distance between the short focus, high aperture objective and the material is quite critical. This causes the need for considerable adjustment as pages are turned, or simply as one page does not lie as flat in the plane as a preceding page. Moreover, the lamp housing containing the illumination means is disposed toward the user, with the concomitant necessity for protecting the user from heated surfaces.
Another approach to the provision of useful viewing devices is shown in Swiss Pat. No. 250,695. This device does not produce a very large image, and the placement of the textual material is awkward. In another approach to assist visually handicapped persons, a closed circuit television system has been used. The television monitor can be adjusted to give a fairly high-contrast enlarged image, and with some modern techniques, an image can be obtained without the need for extremely high intensity lighting. Unfortunately, such systems as are presently available are relatively high-cost and they require considerable and relatively expensive maintenance in use. Further, if it is required to reproduce text or illustrations in color, the cost and maintenance problems are very considerably more expensive than even a monochrome system.
Other art showing approaches to reproducing transparencies or opaque materials or to positioning materials for projection are shown in Brietzke U.S. Pat. No. 2,685,227; Draeger U.S. Pat. No. 2,163,593; Degnan U.S. Pat. No. 2,556,871, and Hanks U.S. Pat. No. 1,821,341.
All of the opaque viewing apparatus up to the present have lacked a combination of ready manipulation of the textual material, low cost, ease of construction and maintenance, and, very importantly, high brilliance and magnification so that persons with impaired vision can readily perceive the images. There is accordingly a need for some system which will permit visually handicapped persons to have convenient access to materials ordinarily read without difficulty by a person of normal vision.